Differential drive mechanism



Oct. 26, 1937. c. F. ALLISON 2,096,834

DIFFERENTIAL Y DRIVE MECHANISM Filed June 8, 1936 2 Sheets- Sheet 1 Oct. 26, 1937. c. F. ALLISON 2,096,334

DIFFERENTIAL DRIVE MECHANISM v Filed June 8, 1936 l 2 Sheets-Sheet 2 Patented Oct. 26, 1937 DIFFERENTIAL DRIVE MECHANISM Charles F. Allison, South Chicago; Ill., assignor I of one-half to John J. Doherty, Dwight, 111.

Application June s, 1936, Serial No. 84,126

2 Claims.

This invention relates to improvements in differential drive mechanisms, and more particularly to a novel system -of differential gearing adapted to be incorporated in the drive of a motor vehicle.

The object of the invention is to'provide a differential drive which will transmit the power of the motor to the rear driving wheels through the usual arrangement of propeller shafts journalled in the rear axle, but in so doing will eliminate certain reaction forces which are detrimental to the proper balance of the vehicle while in motion. 1

It is a well known fact that in the standard type of differential drive mechanism as now employed in motor vehicle construction, the transmission of the power of the motor through the differential mechanism to the rear wheels, there is exerted a torque acting about the rear axle in a direction tending tolift the front end of the vehicle from the ground, this tendency becoming more pronounced as the speed of the vehicle is increased, thus making it difiicult to control the direction since there is less weight tending to hold the front wheels to the road and to respond to the steering mechanism.

The differential mechanism about to be set forth is calculated to eliminate the undesirable torque forces and to create what may be termed a balanced drive.

Referring to the accompanying drawings,

Figure 1 is a view in vertical cross section through the differential mechanism, as taken on line l-| of Figure 2.

Figure 2 is a view in vertical section through the differential housing as taken on line 2-2 of Figure 1.

The drive herein disclosed follows up to a certain point the standard differential drive mechanism and comprises in general a differential housing I located centrally of the rear axle as sembly including the rear axle housings 2, 2 extending laterally from either side of the differential housing I. Extending axially of the rear axle housings 2, 2 are the axle propeller or driven shafts 3, 3 connected at their outer ends with the rear driving wheels in the usual manner, and having rigidly mounted at their inner ends beveled gears 4, 4 facing each other at the center of the differential housing. Surrounding the inner ends of the propeller shafts 3, 3 is a spider 5 having tubular extensions 5 5 mounted in bearings 6, 6 located at the inner ends of the rear axle housings 2, 2, and in turn forming bearings for the inner ends of the propeller shafts 3, 3.

Integral-with the spider 5 is an annular ring-like bearing 5 surrounding the beveled. gears 4, '4

and supporting a pair of beveled pinions "l, 1 disposed diametrically opposite each other and meshing with thebeveled gears 4, 4. Also carried by the spider E is a large ring gear 8 bolted I to a radial flange 5 of said spider 5 and offset to one side of the central longitudinal plane of the difierential housing.

Now the annular bearing 5* of the spider 5 forms the radial bearing for a still larger and auxiliary spider 9 consisting of a ring supporting at angular positions 90 apart, a group of four beveled pinions I9 mounted on axles ll extending radially of the auxiliary spider 9 and journalled in suitable bearings provided therein.

This group of four beveled gears 10 are posi-.

tioned to mesh with the ring gear 8 carried by the inner-or primary spider 5, and immediately opposite said ring gear 8 is. another ring gear: I2 also meshing with the group of four beveled gears II], but this ring gear I2 is stationary, being bolted to one side of the differential housing by means of bolts I 2 Referring further to the outer or auxiliary spider 9, the same also carries about its periphery a large ring gear l3 which meshes with a worm l4 carried by a drive shaft [5 supported in a suitable bearing member [6 integral with the differential housing. The drive shaft I5;extends forwardly in a generally horizontal direction and through the usual arrangement of universal joints is connected through the transmission to the crank shaft of the motor. For the purpose of this disclosure, a worm type of drive is shown, although any other type of drive would be equally effective, as for examplethrough spur, spiral or beveled gearing.

In describing the action and the application of forces in transmitting power through this mechanism, attention might first be called to the fact that if the power from the drive shaft l'5 were delivered directly to the ring gear 8, as for instance through one of the beveled gears ill, the mechanism would then correspond very closely to the standard difierential drive mechanism, but as has already been pointed out, two intermediate elements have been added, namely, the secondary spider 9 carrying the beveled gears l0 and the fixed or stationary ring gear l2.

Now considering the forces acting in transmit ting power through the standard differential drive, it is obvious that as the propeller shafts 3 rotate in a direction to drive the car forwardly, the spider 5 and the pinions l, I carried there- 'by will rotate in the same direction. Now, if

power is delivered directly to the spider 5 by a driving gear member meshing with the .ring

gear 8 and the load on the rear wheels is in- V creased, a condition is approached wherein the wheels tend to be brought to a standstill and the power otherwise delivered from the motor to the differential mechanism for driving .the rear wheels is delivered or absorbed by 'thesupporting structure as a torque. Thus it will appear that as the load on the wheels increases, tending to oppose their rotation, a stalling torque is applied,

to the wheels and there will be a tendency for the ring gear 8, to remain stationary and the power transmitting'or driving gear members l 7 H to ride or climb upwardly on the face of this ring gear. However, these gear membersor pinions I0 mesh with the stationary ring gear" fixed to the differential housing and therefore this climb- 9 ing tendency can only be excited as a torque V V acting about the rear axle of the vehicleand-in an upward direction, that is to say, in a direction to lift the'front end of the vehicle from the road surface. And actually this is what takes place in the standard motor vehicle, the effect being par ticularly noticeable'in the lighter makes, ina's- V a much as there is not the same amount of weight.

to' oppose and counteract the torqueaction as in the heavier'vehicles and therefore greater difficultyi in steering and less control are experienced.'

Now, referring to the improved. differential drive, if a secondary spider and beveled pinions are interposed between those parts that constiture the primary or standard differential drive mechanism and the driving shaft, andfurthermore, afixed ring gear is mounted on the difspeed of a vehicle increases), the tendency of V,

the beveled gears I07 to climb 'the'ring gear 8 is opposedby an equal force tending to restrain said beveled gears from climbing, this restraining force being exerted by the stationary ring gear I2 on said beveled gears. Consequently the reaction forces accompanying the transmission of power through the differential mechanism to the driving wheels are balanced and placed in e'quilibriumiso that there is no torque transmitted to the frame of the vehicle to oppose the even distribution of the wei'ght'o'n all fourrwheelsy V and thus affect its riding qualities or' ability to hold the road, regardless of the speed at which it is driven.

,Having set forth a' preferred embodiment of my invention,

V I claim:

'1. In a differential drive mechanism, the com-1 bination with a differential housing and rear axle assembly including a pair of driven shafts and a drive shaft, of primary and secondary systems of differential gearing mounted in said housing,

said primary systemin'cluding a spider having a ring-gear and said secondary system comprising a spider journalled onthe spider of said primary pinions meshing with said ring gear, and a fixed ring gear mounted on said housing and also meshing with the beveled pinions on said secondary spider, the latterr having driving connection with said driving shaft.

7 system and carrying radially disposed beveled 2. In a'differential drive mechanism, the lcombination with a differential housing and rear axle assembly inclu'ding'a pair of driven shafts and a drive shaft, of primary and secondary systems of differential gearing mounted in said housing,

said primary system including a spider having a ring gear with beveled teeth, a 'ring gear 'corresponding to said first mentioned ring gear fixed to said housing, a secondary spider mounted to rotate on said first mentioned spider and carrying a group of radially disposed beveled pinions meshing with said ring gears, said secondary' spider having peripheral gear teeth meshing with a toothed driving member on said driving shaft.

' CHARLES F. ALLISON. V 

